Process of preparing cellulose butyrate



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GUSTAVUS J. ESSELEN, JR, 0F SWAMPSCOTT, AND HARRY S. MORK, OF SOUTHBOSTON,

MASSACHUSETTS, ASSIGNORS TO ARTHUR D. LITTLE, INCORPORATED, 0F CAM-BRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

PROCESS OF PREPARING CELLULOSE BUTYRATE.

No Drawing. Application filed July 26,

To all whom it may concern:

Be it known that we, (1) GUSTAVUS J. Es- SELEN, J r., and (2) HARRY S.MORK, citizens of the United States, residing at (1) Swamp scott, (2)South Boston, in the counties of (1) Essex, (2) Suffolk, and State ofMassachusetts, have invented certain new and useful Improvements inProcesses of Pre paring Cellulose Butyrate, of which the following is aspecification.

In our copending application filed April 10, 1920, Ser. No. 372,969, wehave described a novel variety of cellulose butyrate and a process ofpreparing the same.

In a general way such process comprises a preliminary impregnation ofthe cellulosic material with a catalyst, such as sulfuric acid, and anorganic acid carrier, followed by an acylating treatment, e. .g. withbutyric anhydrid and butyric acid. In the specific embodiment of theprocess as claimed in our aforesaid application, butyric acid is used asthe carrier for the catalyst employed in the impregnating step.

The present application is concerned with the use of another carrier forthe catalyst, which is described but not specifically claimed in ourcopending 'application, namely acetic acid.

As stated in our copending application, we prefer in carrying out thepreliminary treatment to use a bath of from 12 to 15 times the weight ofthe cellulose. The latter may be in any convenient form, such as cottonroving, yarn, linters, rags, etc., or in the form of wood pulp), paper,etc. It may con- 'tain a certain percentage of moisture, say 3 to 8 percent. The proportions of the ingredients used in the preliminary bathmay vary Within certain limits, and the following example is to beconstrued purely as illustrative and not as a restriction of the scopeof the invention. A suitable preliminary bath may comprise a mixture ofsulfuric acid (sp. gr. 1.84) 1.0% to 5.0%, Water 5.0% to 8.0%, and thebalance, 94.0% to 87.0%, acetic acid.

In certain operations we have conducted, we have obtained efiicientresults with 4.0% of the catalyst. In general, however, the speed of thereaction depends on the amount of catalyst used. Much higher proportionsof the sulphuric acid may be used, the par ticular amount chosendepending to a large Specification of Letters Patent. Patentad A 1 1g.15, 1922.

1920. Serial No. 398,997.

degree on the proportions and kind of the other constituents in thepreliminary bath and the acylating bath.

Similarly the water content is quite varia ble. Preferably from, 5.0% to8.0% is present, but the pro-portion may considerably exceed this rangewithout harm.

After thorough impregnation of the cellulose with the catalyst, theexcess of the solution containing the catalyst is removed in anysuitable manner as, for example by pressing. The impregnated celluloseis then subjected to the action. of the acylating bath composed ofbutyric anhydrid mixed with butyric acid. As an acylating bath, We havefound the following very suitable, but it is to be understood that we donot limit ourselves to the specific proportions named. For each 100parts by weight of cellulose (calculated on the untreated cellulose), wemay employ 465 parts butyric anhydrid (90.0%) and 400 parts butyricacid.

If the proportions of the various materials have been properlyregulated, there will be a rise in temperature which can be readilycontrolled and which need not exceed40 or 50 C. The reaction is allowedto proceed until the product has the desired solubility. If the sulfuricacid employed in the preliminary bath has been used in relatively smallproportion, it is advisable, after a test sample shows good solubilityin chloroform, to add sulfuric acid to the butyrating mixture. For thispurpose a mixture made up substantially of 5.0% sulfuric acid (sp. gr.1.84), calculated on the weight of the cellulose employed, and from 3.0%to 5.0% of water by volume of the butyrating bath is suitable; but theproportion of acid added may of course be varied. Thisaccelerates thetransformation and produces the desired solubility in benzol anddenatured alcohol with less degradation of the product than if thereaction is allowed to proceed for .a longer time without this addition.

As stated in the original application the product is soluble inchloroform, acetylene tetrachloride, acetone, ethyl acetate, 90%carbolic acid, hot denatured alcohol, hot benzol, andat room temperaturein mixtures of alcohol, either ethyl or methyl,.with benzol, containingfrom 50.0% to 95.0% by volume of benzol. It is also soluble in mixturesof 75.0% carbon tetrachloride and 25.0% by Volume of denatured alcohol,and in hot solvent naphtha. It is not soluble in normal butyl alcohol,solvent naphtha or carbon tetrachloride at room temperature.

1. The process of preparing cellulose butyrate which comprisessubjecting cellulose to a preliminary impregnating bath containing anacid catalyst, a carrier therefor comprising acetic acid, and water, andbutyrating the impregnated cellulose.

2. The process of preparing cellulose butyrate which comprisesimpregnating cellulose in a bath containing substantially 1.0% to 5.0%sulfuric acid, the remainder of the bath consisting of acetic acid andwater, and butyrating the impregnated cellulose.

3. The process of preparing cellulose butyrate which comprisesimpregnating cellulose in a bath containing substantially 1.0% to 5.0%sulfuric acid, 5.0% to 8.0% water and the remainder acetic acid, andbutyrating the impregnated cellulose.

4. The process of preparing cellulose butyrate which comprisesincorporating with cellulose an acid catalyst associated with aceticacid as a carrier, and subjecting the treated cellulose to an acylatingbath containing butyric anhydrid and butyric acid.

5. The process of preparing cellulose butyrate which comprisessubjecting cellulose to a preliminary impregnating bath comprising acatalyst and a carrier therefor comprising acetic acid, and water, andsubjecting the impregnated cellulose to an acylating bath containingsubstantially 400 parts butyric acid and 465 parts butyric anhydrid(90%) for each 100 parts by weight of cellulose.

6. The process of preparing cellulose butyrate which'comprisesimpregnating cellulose in a bath containing substantially 1.0% to 5.0%sulfuric acid, 5.0% to 8.0% water and the remainder acetic acid, andsubjecting the impregnated cellulose to an acylating bath containingsubstantially 465 parts of butyric anhydrid (90%) and 400 parts butyricacid for each 100 parts by weight of cellulose.

7. As a new product, a cellulose butyrate such as can be produced by thedescribed process comprising impregnating cellulose in a bath'containingsubstantially 1.0% to 5.0% sulfuric acid, 5.0% to 8.0% water and theremainder'acetic acid, and subjecting the impregnated cellulose to anacylating bath containing substantially 465 parts of butyric anhydrid(90%) and 400 parts butyric acid for each 100 parts by weight ofcellulose.

In testimony whereof, We aflix our signatures.

GUSTAVU-S J. ESSELEN, JR. HARRY S. MORK.

